The goal of these studies is the identification in human material of secreted proteins that are demonstrably endometrium-specific and epithelium-specific and preferably also hormone-sensitive or cancer-related. Ideally, such protein(s) should also be quantifiable in serum as specific marker material for malignant disease. We have studied uterine secretions obtained in vivo, the secretions of isolated endometrial glands incubated in vitro in protein-free medium with and without steroid hormones, and the protein secreted into protein-free media by cultures of authentic endometrial cancer cell lines. We have applied a highly sensitive staining method and a computerized analytical program to the O'Farrell method of two-dimensional chromatography. By these means, we have identified two groups of progesterone-sensitive proteins (peak III and 45K) and a group of proteins found only in the cancer cell media (30K). Recent methodological experiments have resulted in improved preparative methods, and these proteins are being purified and pooled from a large number of samples now in storage. When an adequate amount of pure material is available, antibodies will be raised for the development of radioimmunoassays, and the proteins will be sequenced in order to synthesize labeled oligonucleotide probes for assessing mRNA production. We are beginning to screen serum samples from patients with and without gynecological malignancies for the presence of these endometrial proteins in order to assess their potential usefulness as diagnostic markers and as predictors of the hormonal sensitivity of endometrial cancers. (1)